The house of the Scorpion by Nancy Farmer

Matteo Alacrán was not born he was harvested. His DNA came from El patrón, lord of the country called Opium--a strip of poppy fields lying between the United States and what was once called Mexico. Matt's first cell split and divided in a petri dish. Then he was placed in the womb of a cow, where he continued the miraculous journey from embryo to fetus to baby. He is a boy now, but most consider him a monster--except for El Patrón. El Patrón loves matt as he loves himself, because Matt is himself.

As Matt struggles to understand his existence, he is threatened by a sinister cast of characters, including El Patrón's power hungry family, and he is surrounded by a dangerous army of bodyguards. Escape is the only chance Matt has to survive. but escape from the Alácran Estate is no guarantee of freedom, because Matt is marked by his difference in ways he doesn't even suspect.